1. Field of the Invention
The present invention relates to an optical communication system and, more particularly, to such a communication system capable of sharing a small number of light sources, located at a central communication point, among a plurality of users for providing bidirectional communication, utilizing optical fibers, between the users and the central communication point.
2. Description of the Prior Art
Light wave communication systems are continuously evolving and becoming more robust. As fiber optics enters the local loop to replace conventional copper conductors, the need arises to make these systems economically attractive for the individual subscriber. One method of minimizing cost is to reduce the number of individual fibers needed to provide two-way (i.e. bidirectional) communication between the subscriber and a central communication point (referred to as the central office). The prospect of communicating in both directions on a single optical fiber is attractive for several reasons: (1) lower cost of fiber cable, (2) ease of deployment and retrieval for portable systems, and (3) doubling of traffic capacity on existing cable lines. One such system is described in the article "Two-Way Transmission Experiments Over a Single Optical Fibre at the Same wavelength Using Micro-Optic 3 dB Couplers" by K. Minemura et al appearing in Electronics Letters, Vol. 14, No. 11, May 1978 at pp. 340-2. The transmission system, as described, utilizes micro-optic 3 dB couplers, a single pseudo-step-index optical fiber, GaAlAs LEDs, conventional Si PIN photodetectors, and TTL interface circuits. Although capable of achieving bidirectional communication, this arrangement requires extensive circuitry at both ends of the communication path, each end also requiring its own light source (LED) which can add significantly to the cost of the system. Many other systems exist which share at least some of these same problems (extensive circuitry, light sources at each end, a separate fiber for each signal direction, etc.).
A need remains in the prior art, therefore, for a bidirectional communication system which is inexpensive and, ideally, does not require an independent light source at each end of the communication path.